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Blood smear

Blood smear

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Blood smear

  1. 1. BLOOD SMEARS RAJESH MOHESS, CLT
  2. 2. BLOOD SMEARS • Peripheral blood smear is a very important tool in the hematology lab • It provides rapid, reliable access to information about a variety of hematologic disorders • Examination of the peripheral blood smear is an inexpensive but powerful diagnostic tool in both children and adults • The smear offers a window into the functional status of the bone marrow • Review of the smear is an important adjunct to other clinical data; in some cases, the peripheral smear alone is sufficient to establish a diagnosis
  3. 3. BLOOD SMEARS • An examination of the blood smear (or film) may be requested by physicians based on medical history or initiated by laboratory staff as part of their protocol • Majority of cases for blood smears are from laboratory protocol • With the development of sophisticated automated blood-cell analyzers, the proportion of blood-count samples that require a blood smear has steadily diminished and in many clinical settings is now 10 to 15 percent or less. • Nevertheless, the blood smear remains a crucial diagnostic aid
  4. 4. BLOOD SMEARS • For a true morphological interpretation, a trained person is required to review the smear, as automation in hematology will normally generalize the morphology • The indications for smear review differ according to the age and sex of the patient, whether the request is an initial or a subsequent one, and whether there has been a clinically significant change from a previous validated result (referred to as a failed delta check). • All laboratories should have a protocol for the examination of a laboratory-initiated blood smear
  5. 5. BLOOD SMEARS • Not all hematological disorder requires a peripheral blood smears for diagnosis. • Some conditions can be diagnosed by other laboratory data also. • For example, Iron deficiency anemia can be diagnosed by MCV, iron and ferritin levels
  6. 6. BLOOD SMEARS • There are numerous valid reasons for a clinician to request a blood smear and these differ somewhat from the reasons why laboratory workers initiate a blood-smear examination. • Sometimes it is possible for a definitive diagnosis to be made from a blood smear. • More often, the smear is an important tool in the provision of a differential diagnosis and the indication of further necessary tests. • The blood smear can have an important part in the speedy diagnosis of certain specific infections. • Otherwise, its major roles are in the differential diagnosis of anemia and thrombocytopenia and in the identification and characterization of leukemia and lymphoma.
  7. 7. BLOOD SMEARS Anemia: • In patients with anemia, physician-initiated examinations of blood smears are usually performed in response to clinical features or to a previously abnormal complete blood count • Laboratory-initiated examinations of blood smears for patients with anemia are usually the result of a laboratory policy according to which a blood smear is ordered whenever the hemoglobin concentration is unexpectedly low
  8. 8. BLOOD SMEARS Hemolytic Anemia: • In the hemolytic anemias, red-cell shape is of considerable diagnostic importance. • Some types of hemolytic anemia yield such a distinctive blood smear that the smear is often sufficient for diagnosis. • This is true of hereditary elliptocytosis, and ovalocytosis. • The presence of bite cells points to a Heinz body hemolytic anemia
  9. 9. BLOOD SMEARS Macrocytic Anemia: • Patients with vitamin B12 or folic acid deficiency, the blood smear shows macrocytes. • It may also show oval macrocytes and hypersegmented neutrophils. • When the anemia is more severe, there may be marked poikilocytosis, with teardrop and red-cell fragments
  10. 10. BLOOD SMEARS Microcytic Anemia: • Blood smear not very significant in diagnosis, although very useful. • Most common cause is iron deficiency anemia which can be diagnosed by other blood tests Sickle cells/Thalassemia: • A blood smear is useful. Usually shows target cells sickle cells
  11. 11. BLOOD SMEARS Thrombocytopenia/Thrombocytosis: • A blood smear should always be examined for patients with thrombocytopenia. • This is done to both confirm the thrombocytopenia and to look for the underlying cause. • Falsely low platelet counts may be the result of small clots, platelet clumping, platelet satellitism or abnormally large platelets
  12. 12. BLOOD SMEARS White Cell Disorders (Leukemia/Lymphoma/Bone Marrow Failure): • The precise disease classification may rely upon evaluation of abnormal circulating cells. • Blood smears must always be examined when there is unexplained leukocytosis, lymphocytosis, or monocytosis or when the flagging system of an automated instrument suggests the presence of blast cells • For example, the presence of Auer rods in a blast form in patients with acute myeloid leukemia
  13. 13. BLOOD SMEARS The role of the blood smear in the diagnosis of leukemia and lymphoma is to suggest: • A likely diagnosis or range of diagnoses • To indicate which additional tests should be performed • To provide a morphologic context without which immunophenotyping and other sophisticated investigations cannot be interpreted
  14. 14. BLOOD SMEARS Summary • The blood smear remains an important diagnostic tool, even in this age of molecular analysis • Physicians may and should request a blood smear when there are clinical indications for it. • The Laboratory technologist should make and examine a blood smear whenever the results of the CBC indicate that a blood smear is necessary for the validation or to further investigate an abnormality • To avoid errors and miss any diagnoses, hematological disorders should be investigated by both clinical data and the peripheral smear
  15. 15. PREPARATION OF A BLOOD SMEAR Principle: • A peripheral smear may be requested by the clinician. • It may also be performed as part of the laboratory protocol from reflex or if there are discrepancies from prior results. • We will discuss the ‘Wedge Smear’ • Smears are prepared by placing a drop of blood on a clean glass slide and spreading the drop using another glass slide at an angle. • The slide is then stained and observed microscopically, mainly to determine differential count and morphology study
  16. 16. PREPARATION OF A BLOOD SMEAR Principle: • A well-stained peripheral smear will show the red cell background as red orange. • White cells will appear with blue purple nuclei with red purple granules throughout the cytoplasm. • A well made, well distributed peripheral smear will have a counting area at the thin portion of the wedge smear which is approximately 200 red cells not touching. • A good counting area is an essential ingredient in a peripheral smear for evaluating the numbers of and types of white cells present and evaluating red cell and platelet morphology.
  17. 17. PREPARATION OF A BLOOD SMEAR Principle: • Functions of the peripheral blood smear are: - provide information for diagnosis - provide information for further testing or to establish diagnosis - used as a guide for therapy - Used as an indicator to monitor the harmful effects for chemotherapy and radiation therapy
  18. 18. PREPARATION OF A BLOOD SMEAR Materials: - Glass slides - Applicator sticks - Capillary tubes - EDTA specimen (smear should be made within 4 hours of blood collection) - Capillary blood specimen collected in heparinized tubes
  19. 19. BLOOD SMEAR PROCEDURE • Mix blood properly • Place a small drop of blood (about 2-3 mm) about 1 cm from the frosted end of a clean slide (slide must be completely clean) • Using a spreader (another slide), draw backwards into the drop of blood (while applying pressure) – maintain an angle of 30-45 degrees
  20. 20. BLOOD SMEAR PROCEDURE • When the spreader touches the blood, allow the blood to spread across the edge of the spreader • Move the spreader forward on the slide (in one smooth motion), so a smear is made approximately 3 to 4 cm in length. • The smear should be half the size of the slide, with no ridges, and a “feather edge” should be toward the end of the smear.
  21. 21. BLOOD SMEAR PROCEDURE
  22. 22. BLOOD SMEAR PROCEDURE • Label the frosted end of the slide with the patient’s last name and first initial, specimen number, and the date • Allow the smear to air dry completely (about 5 minutes) • Specimen can now be stained
  23. 23. BLOOD SMEAR PROCEDURE
  24. 24. BLOOD SMEAR Good smear A good smear should have the following appearance: • Appear smooth and uninterrupted • Start thick and gradually thinning out (feather-edge) • The film should take up ½ to ¾ the length of the slide
  25. 25. BLOOD SMEAR LIMITATIONS • The angle between the slides is dependent upon the size of the blood drop and viscosity of the blood. The optimal angle is 45 degrees • The larger the drop of blood and lower the hematocrit, the higher the angle needs to be so the blood smear is not too long • Blood with a higher hematocrit needs to have a lower angle so the smear is not too short and thick • Glass slides must be clean; otherwise, this results in imperfect distribution of cells and improper staining • Smears should not be made from blood remaining on the tube stopper as the lubricant on the stoppers can interfere with the drying process
  26. 26. BLOOD SMEAR LIMITATIONS • Once the drop of blood has contact on the slide, the smear needs to be made immediately. • Otherwise, the blood will clump and dry, again resulting in uneven distribution of WBC and platelets (granulocytes will accumulate at the edges)
  27. 27. POOR SMEARS Poor smears can results from a number of reasons, such as: • Too large or small blood drop • Not pushing the spreader in an even motion • Pressing down heavily on the spreader • Too great or small an angle of the spreader • Speed of stroke used to move the spreader • Clots in the blood • Dirty (oily) slides
  28. 28. BLOOD SMEAR
  29. 29. BLOOD SMEAR
  30. 30. BLOOD SMEAR THE END

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